1. Field of the Invention
The present invention relates, in general, to plumbing, and in particular, to valves for use in hot water supply systems.
2. Information Disclosure Statement
It is often desired to have hot water flow almost instantaneously, i.e., within five seconds, from a hot water faucet after the faucet is turned on. Not only is such instantaneous supply of hot water convenient, it also is ecologically sound because little water is wasted while waiting for the water to become hot. Well-known solutions for this problem include circulating pumps to circulate hot water throughout a hot water system, multiple hot water heating tanks throughout a building, and gravity flow hot water recirculating systems that create a natural circulation of hot water throughout a building by using the natural rise of heated water and the natural sinking of water as it cools.
In such a gravity flow hot water recirculating system, heated water rises from a hot water heating tank to faucets or other fixtures at higher levels and then, as the heated water cools, it sinks and returns to the hot water heating tank through a return line.
However, when the faucets or other fixtures are opened, it is desirable that only the heated water flow to the faucets and that the cooled water in the return line not flow to the faucets. Additionally, if water in the bottom of the hot water heating tank is allowed to flow back through the return line toward the faucets, sediment within the bottom of the hot water tank will tend to be carried out of the hot water tank and into the hot water system.
It is therefore desirable to have a check valve for use in a gravity flow hot water recirculating system that can prevent the backward flow of cooled water within the return line of the system and also thus reduce the flow of sediment into the hot water system from the hot water tank.
Attempts in the prior art to create check valves to solve this problem have been found to cause "hammering" noises of water in the water pipes, and have also been found to create "heat traps" within the valves, thus disturbing the recirculating flow of hot water within the hot water system.
A preliminary patentability search in Class 137, subclasses 337 and 468, produced the following patents, some of which may be relevant to the present invention: Peters, U.S. Pat. No. 2,842,155, issued Jul. 8, 1958; Welty et al., U.S. Pat. No. 3,340,899, issued Sep. 12, 1967; Gross et al., U.S. Pat. No. 3,428,251, issued Feb. 18, 1969; Walton, U.S. Pat. No. 3,556,124, issued Jan. 19, 1971; Hasty, U.S. Pat. No. 3,929,153, issued Dec. 30, 1975; Allison, U.S. Pat. No. 3,938,741, issued Feb. 17, 1976; Tarnay et al., U.S. Pat. No. 4,210,284, issued Jul. 1, 1980; Dinh, U.S. Pat. No. 4,557,252, issued Dec. 10, 1985; and Cromer, U.S. Pat. No. 4,681,088, issued Jul. 21, 1987.
Hasty, U.S. Pat. No. 3,929,153, describes a well-known gravity flow hot water circulating system including a thermal check valve having a float with a specific gravity between 1.05 and 2.0, and the Hasty patent is fully included herewithin by reference. However, the valve disclosed in the Hasty patent does not have an outlet port below the inlet port, and thus can cause significant heat trapping within the hot water system, thereby reducing the circulation of the hot water.
The inventor is also aware of the following references, some of which may be relevant to the present invention: Nash, U.S. Pat. No. 4,191,205, issued Mar. 4, 1980; Karpenko, U.S. Pat. No. 4,410,007, issued Oct. 18, 1983; George, II, et al., U.S. Pat. No. 5,236,010, issued Aug. 17, 1993; Watts Regulator Co., Hydronic Heating Specialties Brochure, (date unknown); Watts Regulator Co., Series 2000 Flow Checks Brochure (date unknown); Watts Regulator Co., Instructions for Installing Watts No. 2000, 2000S (date unknown); and Polymer Corporation, 5 Things You Should Know About Polymer Corporation's General Purpose Acetal Rod and Plate Machining (1992).
None of these references, either singly or in combination, disclose or suggest the present invention.